A blacklist (or black list) is a list or register of entities or people who, for one reason or another, are being denied a particular privilege, service, mobility, access or recognition. As a verb, to blacklist can mean to deny someone work in a particular field, or to ostracize a person from a certain social circle.

Conversely, a whitelist is a list or compilation identifying entities that are accepted, recognized, or privileged.

The term blacklisting may be used in a pejorative sense, implying that a person has been prevented from having legitimate access to something due to inappropriate covert actions of those who control access. For example, a person being served with a restraining order for having threatened another person would not be considered a case of blacklisting. However, somebody who is fired for exposing poor working conditions in a particular company, and is subsequently systematically blocked from finding work in that industry, is described as having been inappropriately and often illegally blacklisted. Blacklisting can and has been accomplished informally by consensus of authority figures, and does not necessarily require a physical list or overt written record.

Blacklisting can be formal or informal. In the employment setting, applicants who apply to numerous positions regardless of being qualified or not can soon be ignored during some or all subsequent applicant processes. This can be an informal choice made by one person or a shared formal response taken up by one office, and not an issue that would be described as blacklisting. In the past, blacklists of union members have been shared or circulated between multiple organizations to prevent hiring of employees who, rather than being incompetent, have been critical of management actions. People have been prevented from working for decades due to being on a blacklist; in some cases the information on the blacklist was false.[1]

According to the Henry Holt Encyclopedia of Word and Phrase Origins the word "blacklist" originated with a list England's King Charles II made of fifty-eight judges and court officers who sentenced his father, Charles I, to death in 1649. When Charles II was restored to the throne in 1660, thirteen of these regicides were put to death and twenty-five sentenced to life imprisonment, while others escaped.

They also point out that "whitelist" is not the opposite of a blacklist, but rather a list, often kept by unions, of people suitable for employment.

Companies which have a payment cardmerchant account terminated, and their directors, are often added to a list referred to when companies apply for an account; they are then unlikely to be granted a new account by any provider. In the US the list is called TMF/MATCH.

Blacklisting by multiple providers is a systematic act by doctors to deny care to a certain patient or patients. It is done in various ways for various reasons; blacklisting is not new. In 1907 the Transvaal Medical Union in South Africa blacklisted patients if they could not pay cash in advance.[2] In this case, there was a physical list kept by the community of physicians. A physical list is not necessary to blacklist patients but the effect is the same.

An infamous systematic blacklist was the Hollywood blacklist, instituted by the House Un-American Activities Committee in 1947 to block screenwriters and other Hollywood professionals who were purported to have Communist sympathies from obtaining employment. It started by listing 151 entertainment industry professionals and lasted until 1960 when it was effectively broken by the acknowledgement that blacklisted professionals had been working under assumed names for many years.[4][5]

Following the passage of California's Proposition 8, Proposition 8 opponents obtained donation lists of those who had supported the ballot measure by contributing to the "Yes on 8" campaign, published the list, organized an activism group, and began calling for boycotts of the places of work of the supporters[6] to force the firing or resignation of employees. Chad Griffin, a political adviser to Hollywood executives and same-sex marriage supporter explained the intent of the campaign by saying, "Any individual who has held homophobic views and who has gone public by writing a check, you can expect to be publicly judged. Many can expect to pay a price for a long time to come."[7] There has been controversy as to whether this is appropriate response to the passage of Proposition 8 on the part of those opposed to it.[8]